Rubber composition and method of preserving rubber



Patented Aug. 7, 1934 UNIED STATES PATENT OFFICE RUBBER COMPOSITION AND METHOD OF PRESERVING RUBBER No Drawing. Application May 22, 1933,

' Serial N0. 672,226

27 Claims.

This invention relates to the art of preserving rubber, either in the vulcanized or unvulcanized condition, synthetic plastics, fatty oils, petroleum products, and like organic materials against unduly rapid deterioration due to oxidation and the like.

It is well known that rubber and other like organic materials are subject to more orless rapid deterioration upon aging, especially when exposed to light, heat, or air. posed to treat such materials with so-called anti-oxidants or age-resisters for the purpose of retarding their deterioration and extending the period of their usefulness. Such previously known anti-oxidants include phenolic compounds, aromatic amino compounds, and the condensation products of aldehydes and amines.

This invention consists in treating the rubber or other like organic material with a member of a new class of extremely effective anti-oxidants. This class comprises the addition products of certain non-accelerating organic amines with hydroxy derivatives of certain aromatic hydrocarbons, and particularly the addition products of primary or secondary amines withv hydroxy derivatives of substances containing at least two discrete aromatic rings, that is, rings which are not condensed to a single conjugated ring nucleus. Such products are readily prepared by combining the amine and the hydroxy compound, preferably in equi-mole'cular proportions or in multiples thereof, by an appropriate method, such as by melting the two constituents together, or by dimolving them separately in an appropriate solvent, mixing the solutions and eliminating the solvent. The addition products, however,

should not be confused with the condensation products made from the same raw materials with the elimination of water. The addition prod- 40 ucts, although they appear to be stable molecular compounds of definite composition, contain all the elements of the constituents, and resemble inorganic salts in that they are more or less readily dissociated into their constituents. in marked contradistinction to the condensation products, which possess fewer atoms than the raw materials, and are comparatively inert and unreactive, not permitting a separation into the two original constituents. It is to be understood, however, that it is not intended to. limit this invention by any theories which may herein be advanced by way of explanation or illustration, but that it is intended that the term addition products" include generally all products obtained It has been pro- 4 by combining phenols with amines without the elimination of water.

The amines which constitute one of the components of the aforesaid addition'products include both primary and secondary, aliphatic and aromatic amines. For example, such aliphatic amines as methylamine, dimethylamine, ethylene diamine, diethylamine, dibutylamine, benzylamine, dibenzylamine, diethanolamine, morpholine, piperidine, and piperazine; or such primary aromatic amines as aniline, toluidine, naphthylamine, diamino diphenyl methane, and p-amino dimethylaniline; or secondary aromatic amines such as methylaniline, diphenylamine, phenyl beta naphthylamine, phenyl alphanaphthylamine, phenyl-p-toluidine, phenyl-panisidine, ditolylamine, symmetrical diphenyl-pphenylene-diamine, symmetrical di-beta-naphthyl-p-phenylene-diamine, dinaphthylamine, methyl alpha naphthylamine, butyl alpha naphthylamine, benzyl alpha naphthylamine, diphenyl ethylene diamine, ditolyl ethylenediamine, p-amino-diphenylamine, p-methylamino-diphenylamine, carbazole, and thiodiphenylamine; or even the aldehyde derivatives of primary amines, which exhibit the characteristic properties and reactions of secondary amines, such as aldol-alpha-naphthylamine, butyraldehyde-alpha-naphthylamine, acetaldehyde-p-aminodiphenylamine; or other primary or secondary amino compounds such as diphenylguanidine may be employed as the basic constituent of one of the above-mentioned anti-oxidant addition products.

The other ingredient, the phenolic compound, which is to be combined with one of the foregoing amines to form the addition product. is selected from the hydroxy derivatives of aromatic-compounds containing at least two discrete aromatic rings. For example, dinaphthol, phenyl-phenol, dihydroxy-biphenyl, p-hydroxy-diphenylamine, dihydroxy-diphenylamine, p-hydroxy-diphenylmethane, dihydroxy-diphenylmethane, p,p',-dihydroxy-diphenyl-dimethyl-methane, p-hydroxy- N-phenyl pyridine, p-hydroxy-N-phenyl-morpholine, etc. may be employed and give rise to products which are extremely valuable anti-oxidants. For convenience, such compounds will practical utilization of the anti-oxidants for the preservation of rubber, since it permits the addition of such anti-oxidants ad libitum or permits changing the proportions employed in any rubber composition to conform to the requirements established by its particular use, without making necessary any change in the proportions of the various vulcanizing agents, accelerators, etc. or in the time or conditions of vulcanization. It is therefore preferred to employ addition products derived from non-accelerating amines, especially secondary aromatic amines, but the addition products derived from other amines are also very useful in cases in which the accelerating properties are not objectionable, or in cases in which it is desired to. employ a single ingredient which functions both as an anti-oxidant and as an accelerator. The addition products are practically odorless and do not impart an undesirable odor to the composition in which they are used. Many of them possess the additional advantage that they show little or no tendency to discolor or stain the rubber or other material in which they are used.

- Rubber or other oxidizable organic materials may be rendered extremely resistant to deterioration by incorporating therein a small proportion of one of the above-mentioned addition products,

preferably in the proportion of from 1,- to 5 parts by weight being added to each 100 parts of the organic material. Rubber so treated withstands oxidation or exposure to sunlight or the elements for a far longer period than similar untreated rubber, without sensible deterioration.

As a specific example of one embodiment of the method of this invention, a typical tire tread composition was prepared containing: blended plantation rubber 100 parts by weight, sulfur 5.5 parts, zinc oxide 30 parts, gas black 40 parts, mineral rubber 10 parts, palm oil 5 parts, and hexamethylene tetramine 0.75 part. is was divided into five portions. one of which was used as a control. To the others were added 1.90 parts (1% of the weight of the composition) respectively of one of the following anti-oxidants, which were prepared by mixing the phenol and the amine in equivalent proportions so that each basic nitrogen reacted with and was neutralized by a phenolic hydroxyl group:

A. o-phenyl-phenol+dibutylamine B. p-phenyl-phenol+piperazine C. p-phenyl-phenoI-I-aniline D. p-phenyl-phenol diamino-diphenylmethane The compositions were thoroughly mixed, and vulcanized in a press for minutes at 145 C. (290 F.) to produce an optimum cure, except the composition containing the product A, which was vulcanized for a somewhat shorter time because of the accelerating nature of the anti-oxidant. The relative rates of aging of the vulcanized compositions were compared by measuring their respective tensile strengths and elongations before and after aging. Accelerated aging tests were carried out in the Geer aging oven, in which samples were maintained at a temperature of C. (158 F.) in a constantly renewed stream of air, as well as in the Bierer-Davis bomb, in which other samples were maintained at the same temperature (70 C.) in an atmosphere of oxygen at a pressure of 300 lbs. per sq. in. In the table below T indicates ultimate tensile strength in pounds per sq. in. and E indicates ultimate elongation in per cent of original length.

Aging tests of addition products It is evident that the composition containing the anti-oxidant retains its good physical properties to a far greater extent than the composition without anti-oxidant, even after a very severe artificial aging test.

' Obviously, the practice of this invention is not limited to the specific compositions given above, such compositions being merely illustrative of one manner of employing the anti-oxidants of this invention. The proportions of the constituents may be varied, or other substances may be substituted therefor, since this invention is applicable not only to pure rubber and rubber compositions of the most varied nature, but also to other oxidizable organic materials. The anti-oxidants may also be applied to the surface of unvulcanized or vulcanized rubber or of other solid materials with good effect on their age-resisting properties, such as by applying them to the surface of the rubber, for example, in solution, or in the form of a paste or emulsion. 1

It is to be understood that the term treating as employed in the appended claims is used in a generic sense to include either the incorporation of the anti-oxidants into the rubber or the like by milling or similar mechanical process, or their addition to the organic material while in a liquid state as by addition to rubber latex before its coagulation, or to the application thereof to the surface of a solid mass of material such as crude or vulcanized rubber. The term rubber is 1 likewise employed in the claims in a generic sense to include caoutchouc, whether or not admixed with fillers, pigments, vulcanizing or accelerating agents.

While I have herein disclosed certain preferred 1 manners of performing my invention, I do not thereby desire or intend to limit myself solely thereto, for, as hitherto stated, the precise proportion of the materials utilized may be varied and other materials having equivalent chemical properties may be employed if desired without departing from the spirit and scope of the invention as defined in the appended claims.

This application is a continuation in part of my co-pending application Serial No. 378,812 filed 1 July 16, 1929, now Patent No. 1,940,817.

I claim:

1. The method of I preserving rubber which comprises treating rubber with the addition product of a phenol containing at least two discrete rings and an amine.

2. The method of preserving rubber which comprises treating rubber with the addition product of a phenol containing at least two discrete aromatic rings and an aliphatic amine. I

3. The method of preserving rubber which comprises treating rubber with the addition product of a phenol derived from an aromatic hydrocarbon containing two discrete aromatic rings and an aliphatic amine.

4. The method of preserving rubber which comprises treating rubber with the addition product of a phenyl phenol and an aliphatic amine.

5. The method of preserving rubber which comprises treating rubber with the addition product of a phenol derived from an aromatic hydrocarbon containing two discrete aromatic rings and an alkyl substituted amine.

6. The method of preserving rubber which comprises treating rubber with the addition product of a phenyl phenol and dibutylamine.

7. The method of preserving rubber which comprises treating rubber with the addition product of a hydroxy substituted biaryl and an amine.

8. The method of preserving rubber which comprises treating rubber with the addition product of a phenyl phenol and an amine.

9. The method of preserving rubber which comprises treating rubber with the addition product of a phenol containing at least two discrete rings and an aromatic amine.

10. The method of preserving rubber which comprises treating rubber with the addition product of -a phenol derived from an aromatic hydrocarbon containing two discrete aromatic rings and an aromatic amine.

11. The method of preserving rubber which comprises treating rubber with the addition product of a phenol containing at least two discrete aromatic rings and an aromatic primary amine.

12. The method of preserving rubber which ,comprises treating rubber with the addition product of a phenol containing at least two discrete aromatic rings and an aromatic diamine.-

13. The method of preserving rubber which comprises treating rubber with the addition product of a hydroxy substituted biaryl and an aromatic primary diamine.

14. The method of preserving rubber which comprises treating rubber with the addition product of a phenol containing two discrete aromatic rings and diamino diphenyl methane.

15. The method of preserving rubber which comprises treating rubber with the addition product of p-phenyl phenol and diamino diphenyl methane.

Disclaimer filed puny.

1, 2, 3, 4, 7, s, 9, 10, i1, 12, 13, 24, 25, and 26.

[Ofiicial Gazette September 17, 1935.]

matic amine. 125

WALDO L. SEMON.

DI so I A| M E R 1,968,914.Waldo L. Semon, Silver Lake Village, Ohio. RUBBER COMPOSITION AND METHOD or PRESERVING RUBBER. .Patent dated August 7, 1934.

August 20, 1935, by the assignee, The B. F. Goodrich Oom- Hereby enters this disclaimer to the claims of the said Letters Patent numbered 16. The method of preserving rubber which comprises treating rubber with the addition product of a phenol containing at least two discrete aromatic rings and a secondary aromatic amine.

1'1. The method of preserving rubber which comprises treating rubber with the addition product of a dihydroxy phenol containing two discrete aromatic rings and an amine.

18. The method of preserving rubber which comprises treating rubber with the addition product of a dihydroxy phenol in which thehydroxyl groups are attached to different aromatic rings and an aromatic amine.

19. The method of preserving rubber which comprises treating rubber with the addition product of a phenol derived from an aromatic hydrocarbon containing two discrete aromatic rings and a diarylamine.

20. The method of preserving rubber which comprises treating rubber with the addition product of a phenol in which two hydroxyl groups are attached to different aromatic rings and a diarylamine.

21. The method of preserving rubber which comprises treating rubber with the addition product of a dihydroxy diaryl alkane and an aromatic amine.

22. The method of preserving rubber which comprises treating rubber with the addition product of p,pdihydroxy diphenyl dimethyl methane and an aromatic amine.

23. The method of preserving rubber which comprises treating rubber with the addition product of p,pdihydroxy diphenyl dimethyl methane with phenyl naphthylamine.

24. A composition comprising rubber and the addition product of a phenol containing at least two discrete rings and an amine.

25. A composition comprising rubber and the addition product of a phenol derived from an aro- 115 matic hydrocarbon containing two discrete aromatic rings and an aliphatic amine.

26. A composition comprising rubber and the addition product of a phenol containing at least two discrete aromatic rings and an aromatic pri- 120 mary amine.

2'1. A composition comprising rubber and the addition product of a phenol containing at least two discrete aromatic rings and a secondary aro- 

